Molecular Genetics of RNA Processing 
and Behavior 
Michael Rosbash, Ph.D. — Investigator 
Dr. Rosbash is also Professor of Biology at Brandeis University and Adjunct Professor of Molecular Biology 
at Massachusetts General Hospital, Boston. He received his Ph.D. degree in biophysics from the 
Massachusetts Institute of Technology and was a postdoctoral fellow at the University of Edinburgh, 
where he studied with J. O. Bishop. Dr. Rosbash was a Guggenheim Fellow in Paris, France. 
MY laboratory is interested in two fundamen- 
tal problems. Our earliest and foremost in- 
terest is the molecular genetics of RNA process- 
ing. For this subject our principal experimental 
system is the budding yeast Saccharomyces cere- 
visiae, which is amenable to both genetic and 
biochemical attack. Our more recent interest is 
the molecular genetics of behavior — in particu- 
lar, circadian rhythms. This problem is addressed 
in the fruit fly Drosophila melanogaster, be- 
cause the organism is amenable to behavioral as 
well as biochemical and genetic approaches. 
Within the area of RNA processing, we are most 
interested in understanding certain aspects of 
pre-messenger RNA splicing, the process by 
which the undesirable sections of a pre-mRNA 
molecule are removed and the remaining 
"sense" sections sewn together. Our interests are 
primarily focused on the more biological aspects 
of the problem. These include how the places in 
the molecule to be cut — the two splice sites in 
the case of a pre-mRNA with a single intron — are 
defined. They also include how splice site 
partners, in the case of a pre-mRNA with multiple 
introns, are specified. 
The latter question is particularly puzzling, be- 
cause most of these splice sites appear similar. 
Yet there is clearly an order to the process, al- 
though the basis for this order is not apparent. 
The adjective "biological" is used to distinguish 
these issues from more "chemical" consider- 
ations, such as how the active site of the splicing 
enzyme is formed and how the efficiency and 
specificity of the splicing reaction are dictated. 
We are addressing these issues of splice site 
definition and partner assignment by examining 
the interactions between a pre-mRNA substrate 
and splicing factors. Although some of the work is 
done in vivo — that is, in intact cells where the 
interactions are inferred from their conse- 
quences — most of our efforts have concentrated 
on interactions that take place during in vitro 
pre-mRNA splicing in a whole-cell yeast extract. 
We have focused particularly on the earliest in- 
teractions, those that apparently reflect recogni- 
tion of the pre-mRNA substrate by the splicing 
machinery. 
Our studies indicate that the factor Ul small 
nuclear ribonucleoprotein (snRNP) plays a prom- 
inent role in these early interactions. Conse- 
quently we have expended considerable effort in 
characterizing this snRNP and its constituents, as 
well as the pre-mRNA-Ul snRNP interaction. Sur- 
prisingly, both ends of the intron interact with Ul 
snRNP, suggesting that certain aspects of splice 
site recognition, if not splice site partner assign- 
ment, are already defined early during the 
spliceosome assembly process, well before the 
cleavage and ligation steps of the actual splicing 
process take place. This work is supported by a 
grant from the National Institutes of Health. 
We are also interested in another biological 
aspect of RNA processing — namely, how mRNA 
is transported from the nucleus, where it is syn- 
thesized, to the cytoplasm, where it is translated 
into protein. This transport problem interfaces 
with the splicing process, since RNA needs to be 
transported to the cytoplasm but usually not be- 
fore the splicing is completed. Otherwise, incom- 
pletely spliced molecules would be prematurely 
transported, which would give rise to untranslat- 
able pre-mRNAs in the cytoplasm. 
The problem of RNA transport is poorly under- 
stood, and even less well understood in yeast than 
in mammalian cells. In yeast, however, there is 
the possibility of addressing the problem with ge- 
netic tools. At present we are localizing pre- 
mRNA and splicing factors within the yeast nu- 
cleus, in an attempt to define a cytological path 
that the RNA may follow in leaving the nucleus. 
The goal is to use existing temperature-sensitive 
mutants and to uncover new ones, both to study 
RNA transport and to define some of the gene 
products important for this process. 
Rhythms 
Our goals in this project are to define the bio- 
chemical machinery that underlies the mysteri- 
ous yet ubiquitous process of circadian rhythmic- 
ity. We are using genetics and biochemistry to 
define candidate genes and gene products that 
may participate in fundamental aspects of these 
rhythms. Our entree into the process is the pe- 
riod gene (per) of Drosophila melanogaster. 
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